This invention relates to electric cable of the type having an assembly of individual conductors, each provided with an insulating sheath, and an overall covering, as well as to a method of manufacturing such cable and an installation for carrying out the method.
Electric cable is customarily made up of a group of insulated wires stranded to form a bunch covered with a jacket. The general cross-section of the cable is circular. In certain cases, the cable comprises a central core of fibrous material, about which the insulated wires are stranded. The group of wires may also be made up of several strands, e.g., of pairs or of quads, which are subjected to a main stranding operation prior to jacketing. If the cable comprises a non-metallic core, it is more flexible and also has greater resistance to tensile stress than cable having a cross-section completely taken up by wires.
Used particularly in the control of devices and machines is flat cable in which the insulated wires are disposed in ribbon form and run parallel to one another. In general, bare wires are embedded in an outer ribbon-like sheath which keeps the wires parallel. The great advatage of this form of cable is that it is easy to find the two ends of any one wire in a length of cable to be connected at both ends, say, between a control device and a machine controlled by the device. In the ribbon which forms flat cable, the different wires are actually placed in a predetermined order. However, flat cable has several drawbacks: it is awkward and often difficult to position within the frame of a machine, in a corner or along an inner ridge between two wall panels. Moreover, the manufacture of shielded flat cable presents major difficulties. Finally, the cost-price of presently available flat cable is higher than for cable having the same characteristics but with conductors bunched and surrounded by a cylindrical jacket.
It is an object of this invention to provide an improved cable which can be cut into any desired lengths, having a structure similar to that of bunched cable but offering the same advantages as flat cable.
A further object of the invention is to provide a method and installation for producing such cable economically.
To this end, the cable according to the present invention, of the type intially mentioned, is formed of successive segments alternately grouped and joined, i.e., in which the conductors respectively present a bunched arrangement and a web arrangement of parallel elements, their sheaths then being joined to one another in a predetermined order over the entire length of these segments so as to permit an IDC.
In the manufacturing method according to the present invention, the individual conductors are unreeled in a web of parallel elements, these individual conductors are stranded alternatingly by groups, each comprising a small number of conductors, the conductors are replaced upon each reversal of the stranding direction in a web arrangement of parallel elements, and the sheaths of the conductors of the web are then joined side by side in such a way as to fix the stranding of the grouped segments, on the one hand, and to constitute the joined segments, on the other hand.
Finally, the installation according to the present invention for carrying out the foregoing method comprises, in a production line, a payout reel for unreeling a web of insulated conductors, a set of two stranding units having parallel axes, a bonding station equipped with several guiding and clamping devices, and a main stranding device situated downstream from the bonding station.